The present invention relates to a gas sensor provided with a protector which protects a sensing element exposed to gas to be detected from being covered with water.
Usually, a gas sensor is known which includes a sensing element in which electric motive forces different in level are generated or an element resistance changes depending on the concentration of specific gas, for instance, NOx (nitrogen oxide) or oxygen in exhaust gas of a motor vehicle. This gas sensor is attached to an exhaust pipe of the motor vehicle and used. When the sensing element is heated or exposed to the exhaust gas of high temperature, a temperature of the sensing element is high. On the other hand, when moisture (water droplet) included in the exhaust gas adheres to the sensing element (the sensing element is covered with water) so that the sensing element receives a thermal shock, there is a fear that cracks or breaks may be probably formed. Thus, to the gas sensor, a protector which covers the sensing element is attached, so that the sensing element is protected from being covered with water.
For instance, in a gas sensor disclosed in patent literature 1, a protector has a double structure including an inside protector with which a sensing element is covered and an outside protector with which the inside protector is covered. In the outside protector, a gas introducing port is formed for introducing exhaust gas to an inner part. An opening area of the gas introducing port needs to be restricted to reduce an entry of condensed water to the protector, however, the opening area for introducing the exhaust gas is necessary to a certain degree. Accordingly, in the gas sensor disclosed in JP-A-2011-145145, the gas introducing port is formed in the shape of a hole elongated in the axial direction of the gas sensor.